What Exactly is a Car Alternator? 4 Questions Answered

What does a car alternator do, and what causes it to go bad or break? Can it drain the car's battery, and how much is a replacement? We help break it all down.

Have you always believed it’s the battery that powers all the electrical components in your car? While the battery provides power when the engine isn’t running and helps start the vehicle, an alternator does the rest. Components such as wipers, radio, and headlights receive power from the alternator instead of the battery. 

An alternator is a critical part of your car’s charging system. Hence, it’s beneficial to know what it is and how it works. Today, we’ll tell you how an alternator operates, factors causing it to go bad, and answer some other frequently asked questions. 

What Does an Alternator Do?

An alternator converts mechanical energy into electricity used by various car components. The electricity generation begins with the engine, as the crankshaft drive alternators in most modern vehicles. However, there might be a separate pulley running from the crankshaft to the alternator if you have an old car. 

An alternator generates electricity as its rotor spins. The rotor has magnets surrounding it, forming a magnetic field. The magnetic field then produces voltage stored by the stator, later reaching the voltage regulator. The regulator then diverts the power to different electrical components in your car and determines how much voltage the battery should receive. 

Here’s a handy, simple graphic of the typical alternator setup in a vehicle, courtesy of emanualonline.com:

Photo: emanualonline.com

What Causes an Alternator to Go Bad?

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Several factors can cause your car’s alternator to go bad. Some of these common reasons include the following. 

1. Dust and Dirt

Dust and dirt accumulating on the alternator can trigger issues. These can instigate shorts or wear on the brushes. However, avoid using a carb cleaner or gasoline to remove dust, as it can damage the thin insulation on wire windings, adversely affecting the magnetic field. 

2. Heat and Oil

Heat and oil exposure to the alternator can be damaging, and it tends to shorten the alternator’s life. Frequently inspect under the hood to notice any leaks and tackle them immediately. 

3. Faulty Components

An alternator consists of different components, and issues with any of them can cause it to fail. Examples include worn-out wires, problems with the ECM computer system, bad fuse, and broken pullet or belt. Problems with any of these parts can affect the power transfer to your car’s electrical components.

Can an Alternator Drain a Battery & How much money is a new one?

Among the different functions of an alternator is battery recharging. However, a bad alternator can also drain the battery. It is because a faulty alternator fails to transfer enough power, eventually draining the battery out. Here’s our article on how long car batteries typically last.

Therefore, next time your battery dies, we advise you to check the alternator for any fault before replacing the battery

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The alternator prices vary according to the brand, size, and amp requirements of your car. Generally, an alternator costs around $130 to $300 or more. However, also consider the mechanic’s charge for installing the alternator. Furthermore, if your bad alternator has drained your battery, you have to worry about replacing it.  


While the battery helps start the vehicle, it does not power all the electrical components in the car. An alternator, part of the car’s charging system, is responsible for producing electricity for wipers, radio, headlight, and other components. It’s made of different parts, such as rotors that spin to produce electricity and transfer it to the voltage regulator, diverting power to the rest of the car.

However, dust, dirt, heat, and oil can damage the alternator, which in turn can drain your battery. A failed alternator would require a replacement, which may cost about $130 to $300, excluding the mechanic’s installation charge.